Whatever Remains, No Matter How Improbable
by xzienne
Summary: Massive Crossover: Supernatural, Doctor Who, Sherlock, Harry Potter When a body is discovered with no visible cause of death, The Doctor pulls together a team of investigators who specialise in the impossible; Sherlock Holmes and John Watson from their universe, and Sam and Dean Winchester. But are they the only ones investigating?


AUTHOR'S NOTE:

This is a massive Crossover Fic inspired by this Tumblr post:

post/90759865809/xzienne-fidefortitude

Featuring Supernatural, Doctor Who, Sherlock, Harry Potter, and a little bit of the Marvel Comic Universe for added insanity.

I can't promise regular updates, but this has been crazy fun enough to keep going with, so we'll see.

Chapter One.

Heathrow Airport, London, England

10th of October, 2013

The plane taxied smoothly into the gate, only thirteen minutes later than the arrivals time predicted. As passengers slowly filed off to collect their luggage and great their families, two brothers peeled away, so-as to not concern any listeners in by their conversation.

"I have fought demons, werewolves, the goddamn Devil and creatures who crawled out of the primordial soup with a Mr. Creosote-sized hunger, but I still cannot make myself calm stuck in a badly ventilated metal tube hurtling across the sky," Dean said bitterly, flexing his fingers to try and ease some blood-flow back to the tips, which had gone white as he gripped the arm rest the entire flight.

"That's just because you're a giant baby," Sam replied, "look, I think this is who we're meeting, here." Without waiting, Sam strode off across the arrivals lounge to where another man stood, next to a window that looked out over the concourse.

"You're the… Baby…" Dean finished lamely, trailing off as he realised Sam could no longer hear him. Begrudgingly, he followed suit.

The man waiting was about Dean's height, watery-eyes hidden beneath what looked to be a fairly regular glower. He stood resting most of his weight on his right leg, but this seemed more out of habit than from any weakness to his posture.

"John?" Sam asked as he approached, and the man turned to face them.

"Ah; so, you would be the Winchesters, then?" the man asked, extending his hand, which Sam took.

"John Watson?" Dean asked, with barely concealed sarcasm. The man's eyes flickered down to a book sitting on the windowsill, and the boys' eyes followed. It was an orange covered Penguin classic of the Complete Works of Sherlock Holmes.

"Yes, yes I believe we all have some explanations due to us, but I'm afraid this is rather going to have to wait. First… well, it probably doesn't do it justice to just say it, you'll need to see it," John replied, looking a mix between nervous and frustrated. Dean opened his mouth to ask something, but Sam cut in.

"Do you have a car?" he asked, and John nodded.

"Yes, follow me, if you wouldn't mind," John turned and led the two boys back to the multi-storey car park, to a waiting black suburban four wheel drive. Sam reached for the front-passenger door, but Dean threw his hand out and caught it first, muscling his bigger, younger brother out of the way with a childishly triumphant smile. Sam's lips pressed into a hard line as he bit back the urge to say something, before stepping back and opening the rear passenger door. John climbed into the driver's seat and the three of them set off.

"So, you mind telling me what the hell is going on?" Dean asked as they pulled out onto the Inner Ring Road West out of the airport and into the city.

"You boys are familiar with a fellow who calls himself 'The Doctor'?" John asked, looking at Sam in the rear view mirror. The boys' faces when stony, as they both realised the seriousness of what was happening.

"Yeah, we know him; he stopped us from ganking a spook outside of New Orleans a couple of months back. Turns out, the bones, and the spook, weren't human; he got it to talk, found the nest, and torched the place when they refused to stop eating people," Dean replied, an edge to his voice that hadn't been there a moment ago.

"Right; so, you know who he is, what he is?" John asked. Sam nodded.

"We know he's a time-travelling alien, doc, you can skip the dance," Sam said, and John nodded.

"Yes, well… Sherlock and I-" John started, pausing as Dean snorted loudly. Sam nodded again.

"Go on," he said.

"Sh- Sherlock and I, we were working a case. A woman had gone missing during a home invasion, seemingly vanished from a steel panic room. The police were treating it as a straight kidnapping, but Sherlock was more interested in the _how_ than the why, and we tracked the manufacturers to a small workshop on the river," John took a left, and they found themselves driving across an area full of parks and lakes. The signs beside the road told them they were heading towards Windsor Castle and Eton College.

"What we found, I don't think we could have possibly prepared ourselves for. The panic room, and as we later found out most of the vaults and bunkers and cells across the country, were actually teleporter – sorry, 'trans-mat' – send/receive platforms, and the makers were staging robberies in homes and banks across the country to force people into them so they could be sent off to somewhere else," John pulled over onto an embankment, looking out over the large, Queen Mother Reservoir. Beside the water, a stretch of land had been cordoned off with white and blue police tape, with three police cruisers and a medical examiners wagon parked around it. In the middle was a white, tarpaulin marquee.

"We never found out where, because that's when the Doctor came in. He told the aliens that the humans who had already been taken were to be released, and the aliens were to leave. They laughed at him, so he simply said to them, 'I am the Doctor'; they scarpered immediately after, and the woman appeared in a cell in Scotland Yard, drugged to her eyeballs but okay."

"What does that have to do with this?" Dean asked, nodding to the scene in front of them.

"The Doctor came to the two of us, gushing about how amazing it was to meet us. It was a little strange, you know; one minute the man is sending aliens running with the sound of his name, the next he's fawning over us like we're the best thing since sliced bread. He told us that he'd come, across from an entirely different universe, because he had a mystery to solve, and that he needed the best. Sherlock naturally agreed, so we were packed up in that Police Box, and brought here, to your world," John finished. Dean snorted again, but Sam merely leant forward.

"Okay; so, where do we come into it?" he asked. John shrugged.

"When we saw the first body, Sherlock got very upset at the lack of evidence. No marks on the body, nothing showed up in the autopsy; but for being dead, the woman appeared to be in perfect health. He said that the death was impossible, and the Doctor lit up; he said that if we needed someone who specialised in the impossible, he could get that. And, so, he got you two." Dean smirked as John finished his explanation.

"Impossible, we can do. Alright, let's see what we've got," he said, gripping the inside door handle, but Sam threw a hand onto his shoulder.

"Wait, Dean; what about our covers? FBI have no jurisdiction over here," he asked, raising his eyebrows. John reached into his coat.

"Sherlock thought of that, so the Doctor got you these; psychic paper, apparently, show whatever you need them to show, as long as the person looking at them haven't been trained to see through the illusion. Sherlock told the local detective, Kerrigan, he was bringing in CIA assistance, and so that's what they'll see," he explained, handing the two wallets over to Sam and Dean. Sure enough, as Dean flipped his open, he saw his own picture next to a realistic CIA badge.

"Agent Lennon; who'd you get?" he asked, looking back at Sam.

"Agent McCartney; well, at least the Doctor has your sense of humour. Come on," he said, and the two of them got out of the car, following John across to the white forensic tent. Inside, they found a small crowd of people; on one side of the tent, talking to each other, stood a pair of men; one was tall, pale and gaunt, with startlingly blue eyes and a mess of curly black hair, the other was shorter and grey-haired. It was towards these two that John led the boys. Sam looked across to the other group, and recognised the Doctor and Clara from their encounters with them several months ago. They were watching intently as the last few denizens of the small tent, the forensic pathologist and her assistant, checked the body for any discernable marks, while a crime scene photographer snapped the occasional shot.

"Inspector Kerrigan; these are the boys from the CIA, here to help out." Watson said as the three of them approached. Sherlock barely nodded in their direction, watching the scene play out in front of him, while Kerrigan looked at the psychic paper identifications the Winchesters handed over.

"I wasn't aware this was a matter for international attention." Kerrigan said, suspiciously. Sam looked to John for help, but the other man was moving across to stand next to Sherlock, and the two were exchanging words in voices too low to hear. Dean leapt in to cover the silence.

"We've… Had… Similar cases in the states; Wisconsin, Washington, Nevada and New Orleans. The Bureau were working the case back home but when victims started showing up here it became a case for the Agency; I expected to meet someone from Interpol…" Dean finished, looking across at the Doctor. Kerrigan nodded, still not convinced, but welcoming the help enough to put the questioning on hold.

"So, you know what this is, then?" he asked, gesturing to the woman. Sam squatted beside the ME to get a better look, and Dean shook his head.

"Not a clue; near as we can tell something is just reaching into their brains and switching them off. We tested EM fields and EEG readings; the whole nine. Still, nothing came up conclusive," Sam replied, over his shoulder.

"Yeah, what he said. Fact is, we never got to too many vics when they were fresh; do you mind if we take a look when you get her shipped back to the morgue?" Dean asked. Kerrigan shrugged.

"I'll need to run your IDs with our liaison with the CIA, but if everything checks out we should be able to get you down there today. Before then, I think you'll want to see the case files."

"Don't bother." Sherlock suddenly said aloud.

"Eh?" Kerrigan said, his face twisting into a grimace of frustration.

"Excuse me?" Dean said at the same time.

"I said don't bother; there's nothing in the files that will tell you anything more than what you see here. We have a woman, aged between twenty-five and thirty, between five foot five inches and five foot nine, brown hair and of average weight. Distinct victim tells us serial killer. Yet, as for why you were brought across, gentlemen, is the fact that she bears not a scratch or bruise or mark of any kind, and as the autopsy will show, exactly like the other two women, there will be no sign of drugs in her system, no strain on her heart, lungs or brain, nothing to indicate a possible cause of death," he rattled off the facts as though he were reading from a sheet on the inside of his eyes, which, given the eidetic memory attributed to the character in the books, he may as well have been. Kerrigan rolled his eyes and threw up his hands.

"Forget it; far go it for a humble copper to argue with the likes of the CIA and MI5. Let me know when you want the body taken away," he snarled, and left. Dean turned to stand next to Sherlock.

"MI5?" he asked, not looking at the taller man.

"It was his idea." John replied, nodding towards the Doctor. The Doctor took that moment as an opportunity, stepping forward.

"Ah, it seems my friends have arrived. Marion, wasn't it, yes, Marion; Marion could you and your lovely assistant step outside for a moment, please? And June, if you could go with them, please; I need a moment to confer with my colleagues." He said, resting a gentle hand on the shoulder of the ME. The three of them smiled and left, as though it were the most normal thing in the world for them to be asked to leave their posts by a man they'd only just met. Sam immediately began to suspect that this case was getting weirder by the second.

"Sam! Dean! So good you could make it; lovely to see you. I see you've already met Sherlock and John," the Doctor said, one hand held up, pointing towards the other two men as he spoke in the broken, lilting way he seemed to always speak.

"Yeah, we've been introduced," Dean said sarcastically, but the Doctor merely smiled wide.

"Hi Sam," Clara said with a wave, and Sam smiled back at her. Dean nudged him with his foot and Sam reacted with a light punch back at Dean's leg before he stood up, but Clara pretended not to notice.

"So, what's the word?" The Doctor asked. Sam shrugged.

"Like you say, no marks on her; I was thinking maybe Wraith, the fear toxin scaring her to death, but there doesn't seem to have been any of the same physiological trauma that would cause, and if it were a wraith surely they'd have fed before the vic died. Certainly not anything else that I can think of; possession maybe, but I've never heard of a ghost or demon that just kills the meat suit," He said, rubbing his chin. Sherlock scoffed.

"What you are describing is simply impossible, none of those… Things, that you mentioned, are real." He drawled.

"Yeah, no shit, Sherlock," Dean said, flashing a smile at Sam, "that's why we're here. Because you're in our world, now, and the creepy crawlies are as real as you're not."

"Yes; as you've no doubt realised, I brought us all together because this case has no immediately obvious answer, and the three of us provide the best knowledge on the crimes of human beings, the crimes of aliens and the crimes of monsters that are available," The Doctor said, reaching out and grabbing Dean and Sherlock's heads, "so somewhere in these melons is the answer to this, and I intend on finding out what."

As Dean was about to try and shrug him off the Doctor span around and pointed once more at Clara.

"Clara, show everyone back to the TARDIS while I speak with Kerrigan. We'll get started as soon as I return."

"Are you sure you should be talking to him on your own? Do you want me to call Kate?" she said with a wry smile. The Doctor frowned.

"I'm perfectly capable of conversing with the constabulary on my own, Clara Oswald… But, yes, letting UNIT know what's happening might be a good idea, even if to stop them stepping all over our investigation," he replied, stepping out.

"UNIT?" Sam asked.

"Unified Intelligence Taskforce; basically the UN's alien hunters." John replied.

"I thought that was SWORD?" Dean asked.

"It's a very, very weird world out there." Clara said with a nod, before gesturing to the others to follow.


End file.
